Fair Power Factor Billing Under Unbalanced and Nonsinusoidal Voltage Supply

Abstract

Utilities apply an additional fee for medium and large customers with low power factors. However, unfair financial charges may occur in installations subjected to voltage unbalance and harmonic distortion. The objective of this paper is to determine the fairest PF definitions and their corresponding measurement algorithms in the case in which a constant impedance load or an induction motor is supplied with unbalanced and nonsinusoidal voltages. Fairness is defined considering that the meter (built based on a particular definition and measurement method) under nonideal supply should lead to very close values as if it was submitted to an ideal balanced sinusoidal supply. We performed computational simulations to emulate several conditions in which a balanced customer (modeled as a constant impedance load or an induction motor) is charged due to a voltage supply no longer balanced and sinusoidal. We also performed experimental tests with an induction motor subjected to a wide range of unbalanced nonsinusoidal supply conditions to ratify the conclusions drawn from the simulations. Based on the simulation results and the experimental tests, we indicate some power factor definitions and measurement methods that are not significantly affected by voltage unbalance and harmonic distortions. These indicated PF definitions provide the fairest billing for conditions with unbalanced nonsinusoidal voltages.

Overview of Power Factor Calculation Method for Nonsinusoidal and Unbalanced Systems

“…Literature [21] indicates that the effective power factor of balanced constant impedance load is not significantly affected by the unbalance of supply voltage. However, in literature [11], the power factor of three-phase induction motor with power factor reference value of 0.95 was tested under the condition of unbalance of supply voltage, and the results showed that the effective power factor would decrease with the increase of the supply voltage unbalance. For example, the power factor decreases to below 0.9 with the supply voltage unbalance increasing to 3%.…”

“…For example, effective power factor is also used in some power quality measuring instruments of FLUKE. However, the power factor calculation method based on IEEE Std 1459-2010 also has some limitations in practical applications, such as the calculation of the power factor of a three-phase balanced user and the calculation of active power [11,12]. New calculation methods based on IEEE standards have also been proposed by some scholars, such as the use of fundamental positive sequence active power [12].…”

Revenue Metering of Unbalanced Prosumers in Energy Communities

“…The apparent power according to [11] was presented as a quantity reflecting the voltage unbalance. However, the authors in [25] showed that the related power factor penalizes customers with three-phase induction machines.…”

An Alternative Methodology for Quantifying Voltage Unbalance Based on the Effects of the Temperatures and Efficiency of Induction Motors

“…In the literature, it is possible to find works whose approaches essentially contemplate the effects of this phenomenon on devices of the power system [1]- [3], and also those in which these effects are used to verify the limitations of the indexes employed in its quantification [4]- [7].…”

“…In [2], it was presented a comparison of the harmonic response of three different efficiency classes of three-phase induction motors (TIM) in the presence of voltage harmonics and unbalance with voltage variations. In [3], an investigation of the influence of unbalanced and nonsinusoidal voltages on power factor definitions and measurement algorithms was made considering a constant impedance load and a TIM.…”